Well you could replace
`
case “Who’s Online Avatars”:
return $translations->translate( “Who’s Online…” );
break;
`
for
`
case “Join Group”:
return $translations->translate( “Follow” );
break;
`
in the example in the link
but as join appears quite a lot of times in buddypress, in different combinations, it might be better just to add your own language file….